Secret to lowering es and sd on a ar10?

[jca57jd]

Hey guys. I built me a ar10 chambered in 243 Winchester a while back. I didn't go cheap on anything in the gun; 26" Kriegar select match grade 1-8 twist, JP buffer assemble, geissele high speed national match trigger, slr adjustable gas block, ect. When I hand load I am extremely ocd. All brass is same length, individually weight sorted with no more variance than 2gr per 100, flash whole debured, primer pockets uniformed, shoulders bumped back .001 from fire formed (.003 in the ar10), .001 neck tension with whiden bushing fl die (.002 in the ar10), bullets sepperated by weight, drop charge .3 grains low on each loading from the chargemaster and then trickle up; my end loads are always as precise as possible. In bolt guns I easily get a sd anywhere from 5-8. The problem I am currently having and can't resolve is my sd and ES with my ar. Is there any secrets your willing to help me on getting the sd and es down on my ar10? The best I'm currently getting is around 17 and I'm using h4350 powder with 105 amax. Thanks!

 

[Kansaswoodguy]

In my 6.5 creedmoor AR-10 I have the best luck with BTHP bullets Lapua Scenars and hornady match bullets avoiding the poly tip bullets or really long nose bthp bullets like the sierra 142 MK. also I seem to get better numbers with Superformance over H4350 in my creedmoor. the shorter ojive to land bullets seem to me to be the best out of magazine fed auto loaders at least to me.

 

[Lefty38-55]

FWIW I always shoot the ladder via the OCW method then look at the chrony figures.

 

[Skytow]

I'm seeing the same thing with my .260 Rem AR. Mine is all top notch components and a Bartlein 24" but... it shoots.

Everything has to be just right. I managed a .339 MOA @ 200 yards 5 shot group but still see SD/ES higher than in the bolt guns. I think it is the nature of the beast so to speak. I've tried everything - neck turning, weighing brass, better dies etc etc but....

So now I am just shooting and enjoying!

How are your groups?

 

[Pdvdh]

Same story in my 5.56 AR15. High ES and SD. ES around 45 is what I'm currently considering good. That after trying 3 different powders and 2 different primers. Rem 7 1/2 primers seem to be helping, compared to Federal 205s. Still working at it, but am ready to call it good.

 

[jca57jd]

I'm getting .5 moa groups at 300 (1.5"). A ES of 40 fps is going lead to a lot of vertical dispersion when I start getting past 700 yards, especially at 1000 yards.

 

[mtwarych]

Are any of the posters here putting a very light crimp on your loads?

My son and I figured out a very light taper crimp does help to settle down the sd and es.

It may have been luck or it was a useful step. We do not have a high quality chrony.

Before we started crimping, we were getting slight setback from the magazine and just a bit more on the chambering. No where near enough setback to raise any safety flags though. Usually 0.0015 or so.

Good luck everybody.

 

[rcoody]

I have been able to get my es down to 10 and sd of 4 in my ar turbo 40 improved

It is an accumulation of a lot of things.

I use lapua brass with br4 primers

custom dies in a co-ax press

clean my brass with an ultrasonic

I anneal every 3 firings

and I weigh charges to 0.02 grains

I believe neck tension and accurate powder charges have had the greatest effect on my SD's

 

[Pdvdh]

I do many of the same things. In addition, I've outside neck turned 3,500 223 cases, annealed all of those case necks, purchased a Forster FL resizing die with a custom ground neck diameter to get rid of the neck expanding ball, weighed all 3,500 cases and eliminated about 8% of the outliers by weight, primer pocket uniformed all cases, flash hole de-burred all cases, weighed all powder charges to +/- 0.1 grain on a RCBS Chargemaster 1500, lubed all case necks prior to bullet seating with either Hornady Unique sizing was or Imperial sizing wax.

I'm currently crimping case necks a little with a Lee Factory Case Crimp die, after seating the bullets, in the effort to see if that helps/hurts. Seems to improve accuracy. Doesn't appear to have any affect on ES/SD.

I shoot all bullets over a triplicate chronograph setup that provides me with 4 recorded velocities for each bullet fired. I've had lower ES/SD when only shooting - say - six rounds over the chronographs. When I shoot 10 or more bullets, the ES/SD inevitably increases. I've had ES higher than 100fps with some powders. Varget is particularly finicky in the .223 case. BL-C(2) is a little better than Varget. Benchmark is better than BL-C(2).

Remington 7 1/2 primers provided a notable reduction in ES/SD with Benchmark powder, compared to Federal 205s.

I'm going to put a little more effort into it, but not much more. I don't shoot this rifle at more than 5-600yds at anything other than paper/rocks.

I'd like to be wrong, but I'm about exasperated to the point of concluding the semi-autos commonly produce higher ES/SD than fixed/bolt action rifles.

 

[rcoody]

well I have a chargemaster

when I quit using it and switched to weighing and trickling on a gempro 250 my es and sd dropped immensely

I use the magnetospeed with a ten round average to calculate my es and sd

 

[FearNoWind]

... I'm currently getting is around 17 and I'm using h4350 powder with 105 amax. Thanks!

Is that your SD or ES? If i's your ES you've got to be holding an SD of about 7 and I'd take that to the bank.

Try to keep in mind that SD & ES are interdependent. Your ES is what controls the SD. So forget about SD and work on ES.
To get an SD of 4 (as claimed herein) you'd have to load for an ES of about 10. That's pretty easy with a bolt gun but I'd expect it to be very difficult with an AR of any variety.

 

[Pdvdh]

well I have a chargemaster

when I quit using it and switched to weighing and trickling on a gempro 250 my es and sd dropped immensely

I use the magnetospeed with a ten round average to calculate my es and sd

Yes, I remember that you prefer to weigh powder charges down to 0.02 gr. I've read your posts on other Threads about weighing powder charges. I'm not critical of that practice. Look at all the time I've spent on 3,500 casings. It's a hobby. I'm glad you shared your approach, and perhaps weighing powder to +/- 0.02 grain would be the additional effort that would drop my ES from 45 down to less than 10. Still not going to do that. I can live with ES 45 in this AR15. It's a plinker.

Here's my perspective. I don't weight powder charges down to less than +/- 0.1 grain for any of my other rifle cartridges, and I rarely experience ES exceeding 100 fps as I have in my AR15, even with the worst load combination tested. And I don't have great difficulty getting ES down to less than 45 fps with a reasonable amount of load development effort.

I've got more time, components, and rounds fired into this effort to reduce ES/SD with my AR15 than I typically expend on any bolt action rifle, and I'm still at ES=45 over 10 rounds fired. The only reason I've put this much time and effort into it was because I was curious. Anyhow, ES = 45 took me a lot of effort, but it's good enough for my intended use of this rifle.

 

[jca57jd]

Is that your SD or ES? If i's your ES you've got to be holding an SD of about 7 and I'd take that to the bank.

Try to keep in mind that SD & ES are interdependent. Your ES is what controls the SD. So forget about SD and work on ES.
To get an SD of 4 (as claimed herein) you'd have to load for an ES of about 10. That's pretty easy with a bolt gun but I'd expect it to be very difficult with an AR of any variety.

17 is my sd. My extreme spread is around 45. My goal is to get es below 20 and sd below 10.

 

[rcoody]

I have no reason to lie. Just trying to help a brother out. the gun is pretty consistent. Here is a copy of the spreadsheet from my magnetospeed. Only 5 shots on this one but somewhere I have others

6mm ar turbo 40 lapua brass br4 primer H4895 28.6 gr lapua scenar L 105 grain Series 1 Shots: 5 Min 2818 Max 2829 Avg 2822 S-D
4.2 ES 11 Series Shot Speed 1 1 2820 ft/s 1 2 2820 ft/s 1 3 2829 ft/s 1 4 2818 ft/s 1 5 2823 ft/s

And the results are here